In the field of demolition, excavation and mining, it is common practice to utilize impact hammers to drive a spade or a pick into the body to separate a portion of it for removal. An impact hammer of this general type is shown in Ottestad patent No. 3,363,512, issued Jan. 16, 1968, which exemplifies a broad range of hydraulically or pneumatically powered hammers. These are sometimes hand held, but more frequently are mounted to a boom for support and manipulation.
These are effective devices validated by long usage. However, they do have significant limitations. One is that very often they simply make a hole. While this does weaken the body and can separate some of it for removal, still getting the material into a bucket usually requires the bucket itself to be used as an impact means. Known buckets are poorly suited to this type of usage.
Another mode of operation is even more severe on the bucket. In this mode, the bucket may or may not have teeth on its digging edge, and that edge is slammed into the body, hopefully to release some material. The problem arises when, as often happens, the bucket does little good on the first blow, and the blow must be repeated. The bucket is raised and slammed down again, but generally it strikes at a different place. This is rarely better than the first blow. The system is simply very inefficient.
Furthermore, buckets are open-faced structures with boundary walls, one of which has the digging edge. Unless they are made unduly heavy, this class of impact to which the bucket is subjected soon causes undesirable deterioration. Often the blow is delivered at a corner, which transmits an eccentric load that must be resisted by even heavier equipment such as larger bearings and cylinders.
As a consequence, equipment utilizing a bucket as part of the release segment of the mining, demolition, or excavation process, is generally inefficient and too large.
It is an object of this invention to provide a bucket with impact means to separate the material without requiring the entire bucket to be involved in the separation part of the process.
This is not a simple objective to attain. For example, it is not optimal to cause the entire bucket to be part of the impact movement, only in part for the reasons described above. Of even greater consequence is the fact that there is a critical relationship between the mass of the driver of the impact hammer itself, and of the total mass to be driven. A light-weight hammer striking a heavy bucket has little effect--much like trying to drive a heavy spike with a tack hammer. Thus, to drive the entire bucket as an impact device would require an impact hammer of excessive mass and bulk. It should be remembered that these buckets are intended to be manipulated, usually at the end of a fairly long boom and often in close quarters. The concurrent requirements of a heavy bucket and a heavy hammer frustrate the construction of a system of useful size.
This invention is able to utilize a conventional bucket, and a sensibly sized impact hammer, by decoupling the impact portion of the hammer from the bucket. In turn, it is necessary to fit the impact hammer into a sensible envelope, and in such a way that it can function to best advantage. While doing so, it is necessary to keep in mind that the effectiveness of an impact blow decreases as the projected cross-section area of the tool increases. Thus, an objective is to keep the projected area small, at least near the working end. This objective is frustrated by the reduced resistance to buckling that results from reducing the cross-section of a long blade which is to exert the impact.
It is an object of this invention to provide the bucket with an impact tool having an optimally small projected area, and which is supported in such a way as to resist binding and buckling forces without excessive binding resistance.
In tests, the bucket of this invention has gone through heavy concrete structures at rates at least several times those which are attainable with known buckets. It has dug at quite rapid rates through deposits such as caliche, which previously known backhoes could not effectively penetrate at all.